Discussion:
Building my own cellphone
(too old to reply)
John Z
2017-09-26 20:27:50 UTC
Permalink
Hey guys (gals?),
anyone here has experience with building their own cellphone or
portable/wearable electronics, to share few tips with me?

My basic idea (and hardware) is:
- rPi
- rPi touchscreen
- sim900
- power stabilizer
- bluetooth dongle
- some kind of rechargeable power supply

All this mounted on a leather bracelet, in a way where bending the bracelet
won't break the PCBs. I'm planning to remove the physical bulk and shred off
some weight by soldering off all the unnecessary connectors (or at least,
mod them to be attachable).

I am unsure how to fit antenna into this. All GSM shields I've seen
come with it, but no modern cellphones have it.

Anyway - shout away! Criticism is welcome :-)
John Z
2017-09-26 20:29:36 UTC
Permalink
Post by John Z
- bluetooth dongle
Sorry, forgot to mention even if its probably obvious - I'd be using
bluetooth dongle + one of those bluetooh in-ears.
superkuh
2017-09-28 00:22:39 UTC
Permalink
I haven't. My personal choice was to abandon the cell network entirely
and operate under ham radio licensing with Ubiquiti 900 MHz
transceivers, custom antenna + poles, and a 25w bidirectional amp at
home. It works okay for around town but it's obviously much more spotty
than a real cell network. The Ubiquiti Nanostation M900s act as a
transparent ethernet bridge from my home LAN to my car. Then that link
is shared to a $15 smart phone (w/cell antenna removed) with a tiny
openwrt wifi router connected to the Nanostation in the car with
ethernet. Everything in the car is solar panel + battery powered.

That said you could check out the ZeroPhone project at,
https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone
because it seems super relevant to you.

Also see the reddit sub,
https://www.reddit.com/r/alternativephones/
Post by John Z
Hey guys (gals?),
anyone here has experience with building their own cellphone or
portable/wearable electronics, to share few tips with me?
John Z
2017-09-28 22:03:32 UTC
Permalink
Post by superkuh
I haven't. My personal choice was to abandon the cell network entirely
and operate under ham radio licensing with Ubiquiti 900 MHz
transceivers, custom antenna + poles, and a 25w bidirectional amp at
home. It works okay for around town but it's obviously much more spotty
than a real cell network. The Ubiquiti Nanostation M900s act as a
transparent ethernet bridge from my home LAN to my car. Then that link
is shared to a $15 smart phone (w/cell antenna removed) with a tiny
openwrt wifi router connected to the Nanostation in the car with
ethernet. Everything in the car is solar panel + battery powered.
That is absolutely *awesome*! I'm stunned! What is your max throughput
and min ping? Is it good enough to, eg. run a video conference?
The spottiness you were mentioning - does this refer to the places where
you don't have a good signal? Mind you, I'm a total noob regarding ham
radios, but this sounds like such a cool setup I'd be easily pressed
into doing something similar.

The reason I went for a custom cellphone was, I'll be honest, divided
between the cool gadget factor and strictly controlled environment.
Obviously, I'll start with some rPi-ready software (I'm thinking ARM
Arch since I already got that running) and probably some glue code to
hook dialing pad and onscreen keyboard with GSM module (works with AT
commands, so this should be fairly simple), but given time (and
motivation/discipline) - I'll probably end up with something much more
customized and tuned.
Post by superkuh
That said you could check out the ZeroPhone project at,
https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone
because it seems super relevant to you.
Also see the reddit sub,
https://www.reddit.com/r/alternativephones/
Thanks for the links. I've done my research on rPi phones but extra
(free) information is always appreciated.


P.S. I'm glad to know I'm not the only one here who abandoned
the cellphones (I'm counting 2 years and 2 months now) - its a sign
I'm at the right place ;-)
superkuh
2017-09-29 00:50:50 UTC
Permalink
Post by John Z
That is absolutely *awesome*! I'm stunned! What is your max throughput
and min ping? Is it good enough to, eg. run a video conference?
The spottiness you were mentioning - does this refer to the places where
you don't have a good signal? Mind you, I'm a total noob regarding ham
radios, but this sounds like such a cool setup I'd be easily pressed
into doing something similar.
Yes. My problems are entirely line of sight and Fresnel zone issues. My
house is below a hill in one direction and the town in general is fairly
hilly and town itself in a valley on all but one side. So I get 5 Mb/s
at 2km in one direction (up to the top of a large hill) but then have it
cut out entirely only a couple blocks from my house in another. I see
ping times of around 10ms. For now it's more of a toy than anything
reliable but maybe someday I can rent out space on a tower.

Because I use a 25w amp (>1w) that means I have to operate under ham
regs (I'm licensed for 'General') and that means *no* encryption. I
think even visiting https websites would technically be illegal.
Complying is most easily accomplished by using the broadband hamnet
firmware and config guides (setting null cypher only in browser, etc),
http://www.broadband-hamnet.org/

If you really want a cell phone functionality then don't do what I did
unless you have tower access.
Post by John Z
The reason I went for a custom cellphone was, I'll be honest, divided
between the cool gadget factor and strictly controlled environment.
Obviously, I'll start with some rPi-ready software (I'm thinking ARM
Arch since I already got that running) and probably some glue code to
hook dialing pad and onscreen keyboard with GSM module (works with AT
commands, so this should be fairly simple), but given time (and
motivation/discipline) - I'll probably end up with something much more
customized and tuned.
The reason I'd want to build my own phone rather than using a mass
manufactured product would be entirely about separating the radio
baseband CPU from whatever hardware I'm using to run userland software.
GSM modules like the pi phones definitely do that. But the age of GSM
(and especially the form implemented in most easy/cheap modules) is
coming to and end soon. I saw (through radio monitoring) when verizon
shut off 1 of the 3 remaining GSM 2 channels in my area just last year.
Most telcos are signaling they'd like to turn GSM 2 off completely in a
couple years.
Post by John Z
P.S. I'm glad to know I'm not the only one here who abandoned
the cellphones (I'm counting 2 years and 2 months now) - its a sign
I'm at the right place ;-)
Unfortunately I haven't completely abandoned cell phones. I still have a
dumb nokia that I take with me on long trips, etc, with the battery out.
But yeah, it's a desirable goal.
pataphor
2017-09-29 11:12:29 UTC
Permalink
On Thu, 28 Sep 2017 19:50:50 -0500
superkuh <***@superkuh.com> wrote:

[...]
Post by superkuh
If you really want a cell phone functionality then don't do what I
did unless you have tower access.
Your project is very cool!

I have been thinking about how to avoid being tracked by cell towers.
What I came up with is some drones that would point lasers at each
other, creating a data connection to my home computer that would not be
easily traceable because laser beams are very narrow.

I don't know about 25W home emitters helping with privacy when ham
licensing also prevents encryption, but recently I bought a cheap FM
radio emitter that was meant to be used in a car so that one could plug
an mp3 player or something into it via a jack plug and the signal would
then be received by the on board car FM radio.

I built a portable 12v power supply out of 8 AA batteries for it using
a cheap standard holder, the same place also sold a car
cigarette lighter adapter (is what the device would normally be plugged
into). The device also had an usbport to plug usb sticks into to play
music directly, and it had another port, probably some microsd thing.

Reception was terrible if I only moved a few centimeters away from it
until I noticed I could plug in an usb extension cable into that usb
port, with some cable working better and others not so much, in effect
that usb cable was an antenna. Now I could walk around the house and
probably even farther and receive pretty good stereo on an old philips
ariaz FM receiver. I had inherited that receiver because the owner
could not establish a connection with a computer to it, it seems to
need a special usb cable, and could not upload songs, but I can
record songs with it now, using the FM radio!

I'm now thinking about using two of these devices (they're very cheap
around 15 euro) and a few rtlsdr equipped laptops to create a data
connection. I have no idea how to encode the data onto stereo audio
though, and maybe I could also encrypt stuff? Maybe the signal is just
too weak to be considered harmful, I mean they sell this stuff for car
audio right? Though maybe that idea of using a short usb cable as an
antenna is too smart to get away with, especially since it broadcasts in
the FM radio spectrum, though I can choose frequencies with .1
megahertz steps and noticed that some frequencies are free, especially
the lowest and highest.

How I would then mount that stuff on a drone would be step 2.

I read about drones that are in development now that can fly for
28 minutes, avoid trees and obstacles and follow and film moving
objects, like a bicyclist or a jogger, but as far as I know they haven't
been equipped with lasers yet.
Post by superkuh
Post by John Z
P.S. I'm glad to know I'm not the only one here who abandoned
the cellphones (I'm counting 2 years and 2 months now) - its a sign
I'm at the right place ;-)
Unfortunately I haven't completely abandoned cell phones. I still
have a dumb nokia that I take with me on long trips, etc, with the
battery out. But yeah, it's a desirable goal.
It seems with just a cellphone number your privacy is already
essentially void. I stopped using them entirely, even though many
organizations just assume one can call them. Some time ago my
health care provider sent me an email telling me they would switch all
communication to their webpage (I don't use webforms or webmail, just
a native mail client) and they would start sending me no-reply
emails to tell me to go there when something new arrived. I could opt
out, no problem, just give them a call :(

P.

Conceited Jerk
2017-09-29 00:59:49 UTC
Permalink
Post by superkuh
That said you could check out the ZeroPhone project at,
https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone
because it seems super relevant to you.
Also see the reddit sub,
https://www.reddit.com/r/alternativephones/
Now *that* is cool! I think I know what I'm doing for my winter project...
--
Am I really conceited? No, but I have every right to be!
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